1. Field of the Invention
The present invention relates to a bearing assembly, and particularly to a bearing assembly which has a sleeve receiving blocks therein.
2. Related Art
Bearings of conventional fans are usually sintered bearings, ball bearings or ceramic bearings. A sintered bearing is made of sintered metallic material, and has many pores. The pores act as lubrication reservoirs, and prevent unwanted leakage of lubricant. Thus the sintered bearing can provide good lubrication. However, a typical shaft is made of highly rigid material. Therefore the surface of the sintered bearing is easily abraded by the shaft, and is prone to have a rather short working life.
A ball bearing can operate without lubrication, and has a longer working life. However, ball bearings are generally costly. In addition, noise generated by a ball bearing increases over its working lifetime as it becomes progressively more worn. When the fan is used in a device such as a computer in a relatively quiet environment such as an office, the ball bearing eventually produces too much noise.
A ceramic bearing has high rigidity, and therefore can operate over a relatively long lifetime. However, ceramic material is highly non-porous. Thus the ceramic bearing is prone to excessive unwanted leakage of lubricant. The contact surface of the ceramic bearing becomes rough after prolonged use without adequate lubrication. Frictional resistance of the ceramic bearing is increased. This makes it more difficult to start the motor of the fan, and decreases the efficiency of operation of the motor.